Nuphar lutea - Yellow Water Lily

Nuphar lutea, or yellow water lily has large floating or emergent heart-shaped leaves that can still be found in the wold in lakes, ponds, and calm and unpolluted rivers. It is less commonly used in ponds than Nymphaea because it is bigger and its golden yellow flower is smaller and less spectacular. However, it does have two advantages over the latter: it can grow in partially shaded areas and is less likely to be eaten by carp.

The yellow water lily belongs to the Nymphaeaceae family, native to Northern Europe, Northern Asia, and North Africa. It is found in calm and deep waters. This robust aquatic perennial can rapidly reach 30 cm (12in) high with a minimum spread of 2 m (7ft). It flowers in July-August. The flower opens in the morning and closes in the evening, lasting for 5 days, a few centimetres above the water, a round, cup-shape with 5 thick yellow petals resembling large buttercups. It measures 3 to 5 cm (1 to 2in). Its light apple-like fragrance with a hint of alcohol attracts insects to pollinate it. The green fruit is shaped like a bottle and releases seeds to be dispersed by water when ripe. The plant has 3 types of leaves:

The first leaves are submerged, light green, with a fine and crumpled texture, reminiscent of lettuce leaves and floating under water. They are not very sturdy, as they are supported by the mass of water. 

Floating leaves, magnificent and huge, heart-shaped, 30 cm (12in) wide: their long triangular petiole brings them to the surface of the water, like the short stem of a bulb. They are dark green and thicker and can spread over 3 to 4 m (10 to 13ft).

The emergent leaves are thicker and slightly smaller and they rise above the water. The water lily will produce this third type after using the available water surface, if the water is not too deep. It offers numerous hiding places for insects and amphibians.

The bottom of a pond is devoid of oxygen and the petioles contain air tubes to supply oxygen to the bottom of the water. They can reach a length of 5 m (16ft) and emerge from a thick rhizome. This aquatic stem grows at the level of the mud and buries its roots in it. The rhizome can reach 2 m (7ft) in length and branch out. In winter, all the leaves disappear, and the plant overwinters in the form of a rhizome.

Nuphar should not be confused with water lilies (Nymphaea), and are hardier. They develop in deeper and colder water and tolerate partial shade. Nuphar has a more wild and less sophisticated appearance and is reserved for large stagnant lakes or ponds. However, a slight current does not harm their growth and flowering.

Nuphar lutea is subject to monitoring and sometimes protection in certain departments, as, despite its vigorous growth, it is sensitive to pollution, and wetland areas are disapearing. If you see the beautiful leaves of this water lily spreading over a pond, it shows that the water is not polluted. The rhizome of the yellow water lily is edible, boiled like a starchy vegetable. It contains tannins and an alkaloid that give it medicinal properties.